Apparatus for making dops to hold precious stones during grinding or polishing



W. I. DAVIDS. APPARATUS FOR MAKING DOPS TO HOLD PRECIOUS STONES DURING GRINDING 0R POLISHING.

APPLICATION FILED DEC.I7, 1920.

w J M Q L l D m g a I W. J. DAVIDS.

APPARATUS FOR MAKING DOPS TO HOLD PRECIOUS STONES DURING GRINDING 0R POLISHING.

APPLICATION FILED DEC-1?, 1920.

Patented Dc.13, 1921.

' 4 $HEETSSHEET 2- W '9- l w W. I. DAVIDS.

APPARATUS FOR MAKING DOPS TO HOLD PRECIOUS STONES DURING GRINDING 0R POLISHING.

APPLICATION FILED DEC. 17, I920.

Patented Dec. 13, 1921.

4 SHEETS-SHEET 3.

w. 1. DAVIDS. APPARATUS FOR MAKING DOPS TO HOLD PRECIOUS STONES DURING GRINDING 0R POLISHING- APPLICATION FILED DEC- IT, I920.

Patented Dec. 13, 1921.

4 SHEETS-SHEET 4- WILLIAM J. DAVIES, 0F AIMSTERDADI, NETHERLANDS.

APPAEATUS FOR MAKING DOES T9 HOLD PRECIQUS STODTLTES DURING GRINDING OR POLISHING.

Specification of Letters Patent. pgypgnted Dem 13 1921 7 Application filed December 1'7, 1920. Serial No. 431,463.

To aZZ whom it may concern:

Be it known that 1, WILLIAM Josnrnns DAVIDS, a subject of the Queen of the Netherlands, residing at '75 l-Veesperzyde, lint sterdam, Netherlands, have invented certain new or improved Apparatus for Making Dope to Hold Precious Stones During Grinding or Polishing, of which the following is a specification This invention has reference to apparatus or appliances for use in making the cast metal dops that are employed for holding diamonds and other gems or precious stones during the operations of grinding or polishing.

In order to properly secure a stone in the apex of a cast conical dop, the said. stone must be accurately set or positioned in the center of the opening at the small or apex end of the conical matrix of the casting mold, and firmly held in that position during the running-in or pouring of the molten (lop-metal, so that the metal at the apex of the dop may run around the girdle of the stone and secure the latter in the appropri ate position, c. with the portion to be ground or polished projecting beyono the end of the dop.

Absolute accuracy in the centering of the stone in the mold is essential in order to insurethat the axis of the stone shall coincide withthe axis of the dop, as otherwise it would be impossiblesubsequently to geometrically grind the required facets on the stone and for the same reason, it is essential that after the stone has been centered in and with relation to the apex opening of the mold it should be rigidly held against any possibility of displacement during the running in of the metal for casting the dop around the girdle of the stone. 7

In the accompanying drawings 1 have shown an apparatus constructed in accordance with my present invention, which onables the above-mentioned essentials to be realized, and which'also has the further and most important advantage that it embodies a self-contained setting tool which is independent of, but attachable to, the mold, or casting part of the apparatus, and provides for the operation of centering the stone being performed away from the mold and in full and convenient view or observation of the operator; the construction of this setting tool and its complementaryparts in the mold being such that when the tool, with the previously-adjusted stone held therein, is applied to the said mold, the said stone is positively and automatically positioned in truly central and perpendicular relationship to the mold axis, without further adjustment being necessary. The apparatus thus enables the setting of the stones and the casting of the same into dops to be carried out more expeditiously andjexactly, and in a more commercially economic manner, than is possible with any known (lop-casting machine, since a number ofsetting tools can be used interchangeably in conjunction with one mold, and the setting or stones in these tools can be effected by one operator or set of operators while the actual casting can be performed by another operator who, as soon as one dop has been made and removed with the stone from the mold, can have another (cold) setting tool, with the stone properly held and centered therein, ready to be placed within the mold for casting the next dop; i

in order to provide for the setting operation to be performed outside or away from the mold, the (lop-casting apparatus in accordance with my said invention comprises two distinct and self-contained parts or units, one of which contains the casting mold and chu mechanism whereby the stone actually held during the casting operation, while the other unit serves as the setting; tool wherein the actual setting of the stone is performed away fromthe mold and whereby also the set stone is positioned r located in the mold matrix prior to being gripped by the chuck mechanism; the-es,- sential' feature'ot the setting-tool unit being that it embodies a memberwhich is adapted to be positioned (when the tool unit is applied to the mold unit) transversely across the mold matrix and is formed with a gap or clearance (hereinafter referred to as the gaging gap) whose shape is a counterpart or replica of the transverse sectional shape of the said matrix. The setting pins of the tool are so arranged in relation to this gaginggapthat they provide for the adjustment of the stone in the axis of the said gap in the same relative position as the said stone is requiredto subsequently occupy in the mold-matrix, while the gap is so disposed in the setting tool member that when the tool is appliedto and located on the mold-unit, it (the gap) will register exactly with the matrix and consequently position the stone correctly in the axis of the latter.

In the said drawings, 7

Figure l is an elevationof my apparatus,

showing the setting tool applied and secured to the mold ready for the casting operation.

Fig. 2 is a plan of Fig. 1. In these views the chuck mechanism are drawn as though I they were located in the same plane as the slot in which the bottom-blade of the setting tool is seated. This, however, is onl done for the purpose of clearly showing the form and construction otth'e chuck mechanism; the jaws being actually located in slots disposed at an angle to the setting tool seating as shown in Figs. 5 and 6.

Fig.4 isa similar view to Fig. 3, but

. shows how the setting tool is applied to the mold for enabling the centered stone to be gripped'and held, during thezactual casting of the dop,.by a chuck mechanism which is embodied in thesaid mold.

Fig. 5 is a plan of the mold, showing the relative dispositions of the'slots or ances provided therein ior'the accommodation, respectively, of the detachable setting tool and of the jaws of the chuck mechanism. -Fig.-.6 is a plan of Fig. 4:.

Fig. 7 is a view showing how, after the setting tool has been applied to the mold and the stone has been gripped by the moldchuck, the upper arm of the said tool is turned into the position indicated, in order to allow for the placing of the pouring gate on the top of the mold. V I

:The same letters of reference indicate corresponding parts in the several figuresjof the draw ngs. V

In theapparatus illustrated, the mold-unit comprises a mold and its supports, chuckmechanism for gripping a stone around its glrdle during the casting operation, and

means. for supporting and registering the setting-tool whereby the previously-adjusted,

stone is introducedinto and positioned in the mold-matrix preliminary to the being taken hold of by the chuck mechanism.

The mold a is elevated on a. suitablestand or frame, with the larger end of: its conical matrixa uppermost, and is arranged so that a detachable pouring gate 2) (see Fig. 7) can be applied to the top of the same to facilitate the running in of the dop metal. The lower or apex end of the matrix has an aperture or opening a of suitable size, in the center of which the stones are first placed by the setting tool and then held by the chuck, and

four vertical slots 0 are cut into, the lower part of the mold,.at an angular separation.

of ninety degrees, to accommodate and provide working clearances for the jaws of the chuck. These slots (as will be seen from the separate plan-view of the mold, Fig. 5) all open at their inner sides into the bottom aperture of the mold, and they are also open at their bottom ends to allow for the jaws of the chuck (which is located underneath the mold) extending upwardly into their respective working clearances.

Another vertical slot clcis cut across the diameter of the mold, and between the chuck-jaw clearances c (in the relative position to the latter as shown in Fig. 5) to accommodate or form a seating for the bottom blade s of the setting-tool unit. This seating is cut right through the wall of the mold on one side-of thematrix toenable the bottom blade of the setting tool (when in situ in the mold) to extend into connection with its external support, whereas on the oppoits side of the said matrirnthe seating slot is out only a sufi'icient distance into the mold walls to afford an adequate bearing for the inner end of the said bottom blade (seeFigs. 4 and 7 On the outside of the mold-stand is arigid bracket c formed with a vertical socket or seating c for the reception of the settingtool standard 8 this socket being disposed so that its center comes exactly in the'same plane as the center of the matrix aperture and the center line of the transverse seatingslot d. i

The chuck mechanism, as has already been stated, is disposedunderneath the elevated mold, and comprises four blade-like jaws 7" having an angular separation of ninety degrees a'ndmounted on the upper-ends of" levers 9 that swing from fulcra in the base of the mold'stand'and are capableof angular movements in their respective'j aw clearances c in the mold; the said levers being operated or controlled by suitable mechanism whereby the inner edges of the blades are (after the position of a stone in the apex aperture of the mold-matrix by the setting tool) closed toward-oneanotherand made simultaneously to project into the said aperture and to grip the said stone at fourequidistant points around its girdle so as to centrally support the same during the casting operation, after which thechuckjaws are separated or opened apart-to release the stone and permit of the latter being lifted out of the mold with the dop.

Any suitable mechanism may be usediior importing the necessary simultaneous and equal angular motions to the chuck-levers for closing together or opening out the awblades. In the apparatus shown in the drawing, however, this mechanism consists of a horizontal cam plate or frame 7 it having four holes or slots h disposed at the same angular separation as the chuck-levers, which are set at an inward inclination to the center of the said plate, and are each passed through one of the holes or slots so that the lowering of the plate will compel the levers to close toward one another whilethe re verse movement will cause them to separate. The center of the plate is connected to a vertical screw 2' which engages with a rotatable nut 2" that has its bearing in base of the mold stand and is rotatable, by bevel or other bearing, from a hand-wheel conveniently disposed on the outside of the stand; the arrangement being such that bv turning the hand-wheel one way orthe other the cam-plate is either raised or lowered for effecting the closing or opening ofthe chuck as desired. 7

To describe now the setting-tool unit .9 of the apparatus: this is a self-contained structure which is applied to the mold only after the setting of the stone has been elfect ed, and it comprises a bottom blade 8' carrying an adjustable bottom centering-pin a a hinged arm a carrying an adjustable top centering-pin and a supporting standard 8 by which the tool is connected or attached to the bracket 6 on the mold-stand, for which purpose the base of the said standard is formed as a peg 8 suitable for dropping into the vertical socket in the bracket.

The bottom blade is rigidly connected with the standard and fixedexactly at right angles thereto. It consists of a metal plate adapted to be inserted from the top into, and to closely and accurately fit within, the bottomblade seating slot d of the mold, and of such a length that, when positioned across the mold matrix, its inner end abuts against the inner end of the seating-slot, as shown in Figs. 4 and 7.

The inner porton of the top sideot' the blade is formed with a V-shaped gaging-gap s" which is a counterpart or replica of the cross sectional shape of the mold-matrix; (see the chain-dotted lines in Fig. 3) the sides of the same having an angle corresponding to pitch or inclination of the sides of the matrix, while the disposition of the gap in the blade is such that when the tool is applied to and properly located on the mold, its edges register with the sides of the said matrix. Consequently a stone which has been correctly adjusted in and relatively to the small end of the gaging gap by the setting tool, prior to the said tool being mounted in the mold will, oi necessity, oc cupy the same relat ve posit on .111 the apex aperture of the matrix when the two parts or units of the apparatus are assembled.

At thebottom of the gaging is a small rectangular clearance s which is or a width not less than the diameter of the bot tom aperture a of the mold matrix, and whose vertical sides preferably have knife or feather edges. This clearance 13 the setting tool counterpart of the said matrix aperture,

and has located centrally within it, a linethreaded screw a which constitutes the bot tom setting-pin and is vertically adjustable pin is carried at its other extremity in such a position that, when. the hinged arm is swung overto bring the same into parallel relationship with the fined bottom blade, the top and. bottom settingpins s 8 are in exactly the same alinement to admit of a stone being held and, centeredbetween-opposite ends. Provision is also made for looking or fixing the hinged arm to the attachment standard afterthe stone has been centered and prior to the tool,-with stone in position,

being transferred tothe mold, for which purpose, a slot 8 may be cut across the crown of the standard, so that on the hinged arm being swung over, a portion of the horizontal limb entersthe cross-slot and is there secured by passing a locking-pin 8 through registering holes in the standard and arm.

The shank of the setting-pin s is slidable in the hinged arm and'is influenced by a I suitablyapplied spring 8 tending constantly to depress the. pin,and inaddition, the said pin hasa screw'adjustment, a part of the shank that extends above the top of the arm beingthreaded and fitted with an adjusting nut. 1

When it is required to introduce a stone between the pins for setting, the adjusting nut is slacked offso that the spring has free play upon the top pin, then the top arm is swung over into parallel relationship with the bottom blade and the extremity of the top pin is held in contact with the end of the bottom one by the springthrust. The locking device (8 is then engaged to secure the two arms in parallel relationship, after which the top-pin s is lifted against the spring to allow the stone to be inserted between the points of the two pins, when the spring exerts a suflicient pressure tolmain- 

